Early clinical trial results suggest drugs acting on a new HIV target are effective, say scientists.

Integrase-inhibitors work in a similar way to existing HIV drugs, by blocking an enzyme essential for HIV to be able to replicate itself.

Scientists are hopeful the new family of drugs will get round the problem of treatment-resistant HIV strains.

Patients who tested one of these drugs, called raltegravir, showed marked improvement, The Lancet reports.

Clinical testing

All of the 178 patients with advanced HIV in the study had being taking regular antiretroviral HIV drugs for about 10 years but were failing to respond to them.

The international researchers measured the amount of HIV genetic material (RNA) in the blood of the patients after 24 weeks of treatment with their usual HIV drugs plus either raltegravir or a dummy drug.

Patients taking raltegravir had an average of 98% drop in their HIV RNA count, compared to just 45% drop in the placebo group.

The number of CD4 cells, which give an indication of the immune response, were also significantly boosted in patients taking raltegravir. And the drug was well tolerated by most of the patients.

Future potential

The study authors, led by Dr Bach-Yen Nguyen or Merck Research Laboratories in Pennsylvania, the US, said: "This drug has the potential to become an important component of combination treatment regimens...for patients failing current therapies with multidrug-resistant virus and limited treatment options."

Resistance to HIV medication is becoming increasingly common - more than one in 10 UK patients with HIV has some level of resistance to at least one drug before they have even begun therapy, a recent study found.

Deborah Jack, chief executive of the National AIDS Trust, said: "Now that many people with HIV are living longer and may be on medication for decades, it is vitally important that new treatments are available to meet any drug resistance that might develop over time.

"With the numbers of people living with HIV increasing worldwide, it is imperative that there is continued investment in new treatments."

Dr Pedro Cahn and Dr Omar Sued, of the Fundación Huesped, Buenos Aires, Argentina, said new therapies would help cut deaths.

But they pointed out that more than 85% of patients living with HIV/Aids around the world still do not have access to regular HIV drugs.